The present disclosure relates to an image display device and a display device including a relevant image display device, and more particularly, to a display device used as a head mounted display (HMD) and an image display device used in a relevant display device.
A virtual display device (image display device) for allowing an observer to observe a two-dimensional (2D) image formed by an image forming device as a virtual image enlarged by a virtual image optical system is well known, for example, from Japanese Patent Application Publication No. 2006-162767.
As illustrated in a conceptual diagram of FIG. 22, an image display device 100′ includes an image forming device 111 having a plurality of pixels arranged in a 2D matrix, a collimating optical system 112, which collimates light output from a pixel of the image forming device 111 into parallel light, and an optical device (a light guide device) 120 on which the parallel light from the collimating optical system 112 is incident, through which the light is guided, and from which the light is output. The optical device 120 includes a light guide plate 121, which outputs the incident light after the incident light propagates through the inside according to total reflection, a first polarizing unit 130 (for example, including a light reflecting film of one layer), which reflects the light incident on the light guide plate 121 so that the light incident on the light guide plate 121 is totally reflected inside the light guide plate 121, and a second polarizing unit 140 (for example, including a light reflecting multi-film having a multi-layer laminated structure), which outputs from the light guide plate 121 the light propagating through the inside of the light guide plate 121 according to the total reflection. A weight and size of a device can be reduced, for example, when the HMD is formed according to such an image display device 100′. Here, reference numerals representing the other components in FIG. 22 can be found with reference to an image display device according to Embodiment 1 which will be described with reference to FIG. 1.
Alternatively, in order to allow an observer to observe a 2D image formed by the image forming device as a virtual image enlarged by the virtual image optical system, a virtual image display device (image display device) using hologram diffraction gratings is well known, for example, from Japanese Patent Application Publication No. 2007-094175.
As illustrated in a conceptual diagram of FIG. 23, an image display device 300′ basically includes an image forming device 111, which displays an image, a collimating optical system 112, and an optical device (a light guide device) 320 on which light displayed on the image forming device 111 is incident and through which the incident light is guided to a pupil 21 of the observer. Here, the optical device 320 includes a light guide plate 321 and a first diffraction grating member 330 and a second diffraction grating member 340 formed by reflective volume hologram diffraction gratings provided on the light guide plate 321. Light output from each pixel of the image forming device 111 is incident on the collimating optical system 112, and a plurality beams of parallel light having different angles at which the parallel light is incident on the light guide plate 321 is generated by the collimating optical system 112, and incident on the light guide plate 321. The parallel light is incident on and output from a first surface 322 of the light guide plate 321. On the other hand, the first diffraction grating member 330 and the second diffraction grating member 340 are mounted on a second surface 323 of the light guide plate 321 parallel to the first surface 322 of the light guide plate 321. Here, reference numerals representing the other components of FIG. 23 can be found with reference to an image display device according to Embodiment 4 which will be described with reference to FIG. 7.